A bit of information which may potentially be useful for others: when I was removing Vista, having booted into it not one single time after almost a year, I was somewhat worried by the fact that the NTFS partition had the "boot" flag set; I didn't want to stop my machine from booting. I was assured that this wasn't what the system used (the MBR is, of course, the important thing) and that this boot flag was only used by Windows itself. This proved to be the case; after removing the NTFS partition it all continued to work as before (and I was able to stretch my ext4 partition from the Live CD).
– Chris MorganJun 4 '11 at 10:38

instead of creating a new partition in place of the old windows one as @Lekensteyn suggests. You can boot into a live-cd and have gparted resize your ubuntu partition to fill the entire drive.
– crasicJun 4 '11 at 17:39

2 Answers
2

These instructions are only valid if you're not using a Wubi installation

Start a disk manager (GParted or Gnome Partition Manager will be fine)

Select the Windows partition (be sure to select the right one!, if you're selecting a partition with the ext* filesystem, you're wrong. A partition with the NTFS filesystem is more likely to be your windows partition)

Remove the windows partition

Windows 7 installs its bootloader to a 100MB partition, the first one. If this partition exists, remove it.

Create a new partition for your data and format it with the ext4 filesystem

If you're using Gnome Partition Manager, you will be offered to take the ownership of the partition. Otherwise, close the partition manager, mount the partition, open a terminal and run:

sudo chown "$USER": /media/name-of-your-partition

Since the windows partition is missing, GRUB's OS prober won't find it when detecting OSes. To remove the windows boot entry, open a terminal and run:

sudo update-grub

This assumes that GRUB is your bootloader which is always the case if you installed Ubuntu after windows 7.

If you've previously configured Ubuntu to auto-mount your Windows partition, you need to remove that. Edit the /etc/fstab file as root and remove the line regarding windows. Beware that you do not remove other lines as it may render your system unbootable which can be recovered with a Live CD only! Such a line may look like:

Edit this new line to have the UUID of your new ext4 partition (type 'sudo blkid' in the terminal to find out the UUID of the new ext4 partition). Also, edit the mount point to something like /media/DATA.

Again, the steps are:

gksudo gedit /etc/fstab

Remove the line about your old Windows partition.

Add a line similar to this one:

UUID=uuid /media/DATA ext4 errors=remount-ro 0 2

Here, substitute uuid with the UUID of your ext4 partition. You can find this from 'sudo blkid' or from GParted, Gnome Partition Manager etc.
4. Save the document and restart.